In a vehicle lamp employed in a vehicle, for example, it is contemplated to provide and employ an elongated light guide member as a side marker lamp (for example, refer to Patent Literature 1). The light guide member is provided in a lamp chamber of the vehicle lamp so that a prism part is formed on a back face all over region in full length, and a surface thereof is oriented to a front side of the vehicle while one end thereof is opposed to a light source. In this light guide member, light emitted from the light source is appropriately reflected on the prism part while being guided in a longitudinal direction and the reflected light is thereby mainly emitted in a radiation direction which is oriented from the prism part (back face) to the surface. In this manner, in the vehicle lamp, the light guide member can be illuminated all over the region in full length to be thereby able to function as the side marker lamp.